As an object detection device mounted on a vehicle, there has been suggested a device configured to collect sounds around a vehicle and detect an object (for example, a vehicle that generates a traveling sound) which is a sound source by using the collected sound information. A device described in Patent Literature 1 is configured to convert acoustic signals output from a plurality of microphones arranged at predetermined intervals into corrected acoustic signals by respectively removing frequency components of a low frequency band and a high frequency band from the output acoustic signals by using a band-pass filter, calculate a power of a predetermined frequency band which exhibits a characteristic of a traveling sound of a vehicle from the corrected acoustic signals, and determine that there is an approaching vehicle when the power level is greater than a predetermined value. Further, the device is configured to convert the acoustic signals into noise-suppressed signals by removing unnecessary noise components from the corrected acoustic signals, calculate cross-correlation between the noise-suppressed signals of the plurality of microphones, and calculate an approaching direction of the approaching vehicle from an arrival time difference in which the correlation is maximized.